I’m not sure how it is in the US, but in the UK we don’t even get taught the grammar of English. No one knows grammatical terms, like preposition, person, the name of tenses, the subjunctive, or even simple ones like verbs, adjective, adverbs and nouns.
When you don’t even know formally how your own language is structured, it is very difficult to learn another language.
For example, my mother (native French-speaker) gives private French lessons. She finds that instead of saying “ok today we’re going to learn about the subjunctive mood, the root is the third person plural of the indicative mood of the verb with the following endings”, she spends most of her time having to explain what those terms mean.
I realise that there may be other ways that are less formal to learn languages, but at the end of the day, grammars follow rules, and if you don’t even understand the rule book in your own language you’re already at a huge disadvantage in my opinion.
All these online articles claiming “don’t worry about grammar, that will come later” are missing out on what I think is the most important tool in language learning.